Vapor transfer

ABSTRACT

In preferred form, an automobile heating and air conditioning system having a plenum chamber containing a heater core and an evaporator core, and a closable purge outlet opening into the passenger compartment. When the heating and air conditioning system is inoperative, the purge outlet allows air to flow through the plenum chamber and into the passenger compartment to prevent the formation of odor and humidity in the chamber. When the system is operative to heat, cool or ventilate the automobile interior, the purge outlet is blocked by a pivotal door which also directs air through a heater outlet for distribution into the passenger compartment.

United States Patent Snyder [151 3,662,818 [4 1 May 16, 1972 VAPORTRANSFER [72] Inventor: John Snyder, Lockport, N.Y.

[73] Assignee: General Motors Corporation, Detroit,

Mich.

[22] Filed: May 11, 1970 [21] App]. No.: 36,078

Primary Examiner-Charles Sukalo Attorney-William S. Pettigrew and JohnC. Evans [5 7] ABSTRACT In preferred fonn, an automobile heating and airconditioning system having a plenum chamber containing a heater core andan evaporator core, and a closable purge outlet opening into thepassenger compartment. When the heating and air conditioning system isinoperative, the purge outlet allows air to flow through the plenumchamber and into the passenger compartment to prevent the formation ofodor and humidity in the chamber. When the system is operative to heat,cool or ventilate the automobile interior, the purge outlet is blockedby a pivotal door which also directs air through a heater outlet fordistribution into the passenger compartment.

5 Claims, 21 Drawing Figures PATENTEUMM 16 m2 SHEET 2 OF 6 ATTORNEY DUCTAI R DISCHARGE PATENTEIIIIIIISIIII: 3.662818 SHEET 6 BF 6 \l L, V 1- y yI 352 6 I 55k I2o- AIR CONDITIONING H0- MODE HEATING MODE -OFF ON ENGINECOOLANT VALVE I RECIRCULATED AIR OUTSIDE AIR AIR SUPPLY A LOWER LEVEL IUPPER LEVERA DUCTS DUCTS +II i BLOWER SPEEDS AUTOMATIC INVEN'IOR. I I II I I 2222 Snyder 0 O I'O 2'O 3'0 4'o 50 60 BY ATTORNEY VAPOR TRANSFERThis invention relates to an automobile heating and air conditioningsystem and more particularly to such a system having means to preventthe formation of odor and humidity.

When prior automobile heating and air conditioning systems areinoperative, stagnant air surrounds the heater and evaporator coreswithin a plenum chamber. Odor and humidity may form in the plenumchamber because of this stagnant condition and because of thedehumidification caused by the cool evaporator core of the airconditioning system. When the system is activated, the discharge of thisaccumulated odor and humid air into the passenger compartment isundesirable.

Another problem with prior automobile heating and air conditioningsystems is heat buildup within the plenum chamber during the period thesystem is inactivated. Because of the plenum chambers close proximity tothe engine compartment, the temperature of air within a closed plenumcan increase significantly. The problem is of course more severe duringthe summer season when an initial blast of hot air into the passengercompartment would be most undesirable. Therefore, it is desirable toprevent the formation of hot air within the plenum chamber prior toactivating the air conditioning system.

The subject heating and air conditioning system includes conventionalheating and air conditioning components such as a heater core and anevaporator core within a plenum chamber, an inlet for admitting air tothe chamber and outlets for passing air back into the passengercompartment. Additionally, the system includes a purge outlet which isopen to the passenger compartment when the system is inoperative tomaintain a continuous flow of air through the plenum chamber. This airflow prevents the formation of odor, humidity and heat in the plenumchamber. Thereafter, when the system is activated, the purge outlet isclosed by a pivotal door which then directs air into the passengercompartment through a heater outlet.

Therefore, an object of the inventor is to provide an automobile heatingand air conditioning system with means to automatically prevent theformation of odor, humidity and hot air in a chamber which contains theheater and evaporator cores while the system is inoperative.

A further object of the inventor is to provide an automobile heating andair conditioning system with a purge outlet in duct work which enclosesa heater core and an evaporator core and through which a continuous flowof air is maintained while the system is inactive to prevent theformation of odor, humidity and hot air within the duct work.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

In the drawings:

FIG. 1 is an elevational view of the front portion of an automobilebroken away and sectioned to reveal the heating and air conditioningsystem of the present invention;

FIG. 2 is a fragmentary elevational top view of the heating and airconditioning system;

FIG. 3 is a vertical front view of the heating and air conditioningsystem taken along line 3-3 of FIG. 2 and looking in the direction ofthe arrows;

FIG. 4 is a vertical end view of the system taken along line 4-4 of FIG.3 and looking the direction of the arrows;

FIG. 5 is a fragmentary sectional view of the purge outlet taken alongsection line 5-5 of FIG. 3 and looking in the direction of the arrows;

FIG. 6 is an enlarged elevational view of the power servo assembly shownin FIG. 1 with its top cover removed;

FIG. 7 is a vertical view of a dash control assembly as would be seenfrom the passenger compartment revealing controls for operating thesystem;

FIG. 8 is a horizontal sectioned view of the dash control assembly takenalong section line 8-8 in FIG. 7;

FIG. 9 is a diagrammatic view showing vacuum components and electricalcomponents of the system which cooperate together to maintain desiredheating and cooling;

FIG. 10 is a schematic illustration of the control vacuum valve shown inFIG. 9 at different settings of the dash control assembly;

FIG. 11 is a schematic illustration of the power servo vacuum valveshown in FIG. 6 at various positions to effect system operation;

FIG. 12 is a diagrammatic illustration of the system showing the vacuumand electrical connections for effecting operation of the purge doorshown in FIG. 4;

FIG. 13 is a sectional view of the electrically actuated vacuum valveshown in FIG. 12; and

FIG. 14 presents a diagram showing the duct outlet tem' perature andblower speed program as a function of the airmix damper position.

The system herein disclosed utilizes vacuum motors to actuate certaincomponents. Such motors are described in the U.S. Pat. No. 2,963,954,granted Dec. 13, I960, in the name of A. D. Baker and in U.S. Pat. No.3,187,640, granted June 8, 1965, in the name of K. W. Young et al. Aservo-valve vacuum controlled air-mix damper is described in the U.S.Pat. application, Ser. No. 236,559, filed Nov. 9, 1962, in the name ofG. L. Rogers and now abandoned. Suitable amplifier circuits which arecondition responsive and taken by themselves are shown to be old in theU.S. Pat. to B. H. Pinckaers, No. 2,945,133, granted July 12, 1960, andalso in the U.S. Pat. to J. W. Gray, No. 2,622,231, granted Dec. 16,I952. Transducers for receiving a signal in the form of a varyingelectrical current and efiecting a corresponding movement in a controlunit such as a valve are known and a specific version thereof asdescribed in the U.S. Pat. No. 3,172,021, in the name of M. J. Manahan,and also in U.S. Pat. No. 3,073,345, granted Jan. 15, 1963, in the nameof N. R. Hagler. A suction throttling valve is disclosed in the U.S.Pat. No. 3,084,521, granted Apr. 9, 1963, in the name of E. S.Schlotterbeck. A thermal vacuum valve is described in U.S. Pat. No.1,871,733, granted Aug. 16, 1932, in the name of E. G. Petersen.Components or separate devices such as the above are utilized in thesystem herein disclosed but they are not herein fully described as theirspecific forms may be varied and are not necessary in setting forth thepresent invention.

In FIG. 1, an automobile 10 is illustrated in outline including anengine 12 having valve covers 14 and an air cleaner 16. The engine 12 ismounted within engine compartment 18 which is separated from a passengercompartment 20 by firewall 22. A radiator 24 for cooling engine 12 ismounted within the front end of engine compartment 18. An instrumentpanel or dash is shown in dot-dash lines at 26 within the passengercompartment 20. Air conditioning components are shown within enginecompartment 18 which include a compressor 28, a condenser 30, adehydrater-receiver 32, a suction throttling valve 34 and an evaporatorassembly 36. The

- evaporator assembly includes a core 38 and an expansion valve 40(partially hidden by evaporator outlet 42 in FIG. 1). These airconditioning components are well known in the art and specific detailsof their structure form no part of the present invention. Therefore, adetailed explanation of their construction is unnecessary.

A heater core 44 is shown adjacent firewall 22. Air flowing through coreis warmed by transfer of heat from the engine coolant. The heater core44 and the evaporator core 38 are enclosed within a duct work 46 whichforms an elongated plenum chamber 48. An air inlet to the plenum isgenerally indicated by the numeral 49. Air inlet 49 includes an openinginto the passenger compartment 20 for receiving recirculated air and anopening to the outside. A pivotal inlet door 50 is normally positionedto admit about 20 per cent outside air and about per cent recirculatedair. A vacuum actuator 51 moves the door 50 against the outside outletto admit per cent recirculated air when actuated. Adjacent the inlet 49and forward of firewall 22 is a blower fan 52 which is rotated by blowermotor 54. Fan 52 draws air through the inlet 50 and into the plenum 48where it flows through evaporator core 38. After the air passes throughthe evaporator core 38, it either flows through heater core 44 orthrough a bypass duct 56. A

pivotal air-mix damper 58 located within the air stream from evaporatorcore 44 proportions the flow of air through the heater 44 and the bypass56 in response to heating and cooling requirements of passengercompartment sensed by the system.

After flowing past the air-mix damper 58, air is directed into an airdistributor duct 62 for distribution into the passenger compartment 20.When the heating and air conditioning system is inactive, air passesthrough a purge opening or outlet 60 into the passenger compartment asbest illustrated in FIGS. 2, 4 and 5. A purge door 64 is pivotallymounted within duct work 62 to alternately allow air to flow throughpurge outlet 60 or through a heater outlet 66. The purge door 64 (seenin FIGS. 4 and 5) is spring biased against outlet 66 to normally directair through purge outlet 60. A vacuum actuator 68 which is operablyconnected to purge door 64 moves the door to a position blocking purgeoutlet 60 and unblocking outlet 66 when vacuum pressure is routed to theactuator 68.

The air distributor duct 62 shown in FIGS. 1 5 has, in addition toheater outlet 66, an air conditioning outlet 72 for the distribution ofcool air through upper level ducts 74 and upper level outlets 76. Adefrost outlet 82 directs warm air through flexible tubing (not shown)to the base of the automobile windshield for defrosting purposes. Air isalternately directed either through the upper level outlets 76 or thelower heater outlet 66 and defrost outlet 82 by a pivotal mode door 84.Mode door 84 is normally held by a spring in a position blocking airflow into the upper level air conditioning duct 74 to direct air throughthe heater outlet 66. A vacuum actuator 86 is operably connected to modedoor 84 to move the door into a position blocking heater outlet 66 anddefrost outlet 82 for unblocking the air conditioning outlet 72 whenvacuum pressure is routed to the actuator 86.

A defroster door 88 is pivotally mounted adjacent the defroster outlet82 to direct heated air therethrough to the base of the automobilewindshield. The defroster door 88 is normally held in the closedposition shown in FIG. 3 by a spring (not shown). During the heatingmode of operation, a part-travel port 89 of a dual position vacuumactuator 90 is supplied vacuum pressure to move the defroster door 88into position 88' shown in broken lines in FIG. 3 thus permitting asmall quantity of warmed air to flow through outlet 82 onto thewindshield. During de-icing and defogging modes of operation vacuumpressure is applied to a full travel port 91 of the vacuum actuator 90which moves the defroster door 88 to position 88" so as to direct alarge quantity of the warmed air through outlet 82 and onto thewindshield.

When the heating and air conditioning system is inoperative, fan 52pumps air through plenum chamber 48. The purge door 64 is normallybiased into a position blocking heater outlet 66 which permits air toflow through the purge outlet 60 into the passenger compartment. At thesame time, the mode door 84 of the air distributor 62 is held by aspring in position blocking the air conditioning outlet 72 and defrosterdoor 88 is held by a spring in position blocking the defroster outlet 82as shown in FIGS. 2 and 3 respectively.

When the heating and air conditioning system is in the maximum heatingmode of operation, the air-mix damper 58 is positioned to block offbypass 56 which causes all the air flow through heater core 44. Duringthis heating mode of operation, vacuum pressure is supplied to the purgedoor vacuum actuator 68 to pivot the purge door 64 into a position whichblocks the purge outlet 60 and opens the heater outlet 66. During thisheating mode of operation, no vacuum pressure is supplied to vacuumactuator 86 and, therefore, mode door 84 is in its normal positionblocking the air conditioning outlet 72. During this heating mode ofoperation, vacuum pressure is applied to port 89 of actuator 90 to movethe defroster door 88 to a part-travel position 88' shown in FIG. 3.

When the heating and air conditioning system is in the defogging orde-icing mode of operation, the air-mix damper 58 and the purge door 64are positioned as set forth above for heating. The mode door 84 ismaintained by a spring in a position blocking the air conditioningoutlet 72. Vacuum pressure is applied to the port 91 of the dualposition vacuum actuator to move the defroster door 88 to its fullyopened position 88" which directs substantially all the air through thedefroster outlet 82 and onto the windshield.

When the heating and air conditioning system is in the maximum airconditioning mode of operation, the air-mix damper 58 is positioned tounblock air flow through bypass 56 and to effectively block air flowthrough heater core 44. Simultaneously, the purge door 64 is moved byactuator 68 to a position which blocks purge outlet 60 and unblocksheater outlet 66. Also, vacuum actuator 86 moves the mode door 84 into aposition which directs air through the air conditioning outlet 72.

The aforementioned energization of the vacuum actuators and resultantpositioning of dampers and doors is controlled by a vacuum-electricalclimate control system schematically shown in FIG. 9. In addition, thissystem regulates the speed of blower motor 54. A dash mounted controlhead assembly 94 shown in FIG. 1 includes a lever 96 which is manuallyset by the vehicle operator at one of the seven positions illustrated inFIG. 7 which is a view of the control head assembly 94 as seen by theautomobile operator. More particularly, the control head assembly 94includes a labeled front face 98 which identifies the seven positions ofthe control system. A knob 100 on the end of lever 96 may be moved bythe operator to the following operating positions: vent, off, low, auto,high, fog and ice. Lever 96 extends through the face 98 and is pivotedabout a pivot post 104 as best seen in FIG. 8. Post 104 extends throughan elongated slot 106 in lever 96 and integral tabs 108 on the end ofpost 104 overlay the lever 96. Lever 96 pivots about post 104 in a pathdefined by the coaction of a pin 110 on lever 96 and a track 112 securedto a base plate 114 of the control head assembly 94.

As lever 96 is pivoted about post 104 from the vent position to the iceposition, a portion of a control head vacuum valve 116 is rotatedapproximately 90 with respect to a portion of the valve affixed to baseplate 114. An upstanding pin 118 on the movable portion projects throughand is engaged by an elongated slot 120 in the lever 96 to rotate thevalve. A nylon insert 121 encircles the pin 118 and reduces frictionbetween the pin and the sides ofslot 120 as lever 96 is pivoted.

Lever 96 supports three insulated conductors 122, 124, and 126 eachhaving a plurality of cantilevered contacts which move with the lever 96and bear against a circuit board 130. The coaction between conductors122, 124, and 126 and the circuit board 130 is best understood byreference to FIG. 9. In FIG. 9, the circuit board 130 schematicallyshows the seven positions of control head assembly 94. Conductors 122,124, and 126 are shown in the auto position it being understood that aslever 96 is pivoted the conductors 122, 124, and 126 move to thepositions corresponding to the dotted lines on the circuit board 130.The enlarged rounded portions 128 of conductors 122, 124, and 126represent the aforementioned contacts which touch the circuit board 130.

The control head vacuum valve 116 shown in FIG. 8 is illustratedschematically in FIG. 9. Valve 116 has eight ports and a vent passagewhich are alternately interconnected as lever 96 is pivoted through theseven operative positions of the control head assembly 94. Port 1 ofvacuum valve 116 is connected by vacuum line 132 to an inlet of a checkvalve 134. The outlet of check valve 134 is connected by a vacuum line136 to a raw vacuum source such as the intake manifold of an internalcombustion engine. The purpose of check valve 134 is to prevent air flowfrom the vacuum source to valve 116 upon failure of the vacuum source tomaintain a predetermined vacuum pressure. A vacuum storage tank 138 isalso connected to the inlet of check valve 134 by vacuum line 140. Port3 of valve 116 is connected by a vacuum line 142 to the outlet of anormally closed electrically actuated valve 144. The purge door vacuumactuator 68 is connected to an inlet of valve 144 by a vacuum line 146.The port 89 of the defroster vacuum actuator 90 is connected to an inletof valve 144 by a vacuum line 148. Port 4 of valve 116 is connected by avacuum line 150 to port 91 of the defroster vacuum actuator 90. Port 5of valve 116 is connected by a vacuum line 152 to the recirculating airvacuum actuator 51. Port 7 of valve 116 is connected by a vacuum line154 to the mode door vacuum actuator 86.

The air-mix damper 58 is positioned by a servo-power assembly 156 shownin FIGS. 1, 6 and 9 to proportion a flow of air through heater core 44and through bypass 56. The servopower assembly 156 has a thin walledhousing 158 which supports a servo vacuum valve 160. Vacuum valve 160 isa rotary valve similar to the control head vacuum valve 116 and has amovable portion with four ports and a vent passage. The moveable portionof valve 160 is rotated by a lever 162 about an axis 164. A second lever166 is supported by housing 158 and is pivoted about axis 164. Lever 166supports insulated conductor plate 168. Conductor plate 168 supportsinterconnected conductor arms (not visible in FIG. 6) on its bottomsurface which are shown schematically as 172 in FIG. 9. A circuit board170 which is secured to housing 158 by a plurality of screws 174, hasinsulated conductor strips 176, 178, 180 and 182 on its surface. Theconductor arms 172 pivot about the axis 164 and slide along conductorstrips 176, 178, 180 and 182. Four resistors 184, 186, 188 and 190 areconnected respectively to conductor strips 176, 178, 180 and 182 tocomplete the switch arrangement schematically shown in FIG. 12. Asconductor arms 172 pivot about axis 164 from one side of housing 158 tothe other, a circuit is completed successively through conductor strip182, through conductor strip 180, through conductor strip 178, throughconductor strip 176, again through conductor strip 178, throughconductor strip 180, and through conductor strip 182.

The vacuum valve 160 is rotated by lever 162 which interconnect itsports and its vent passage in response to the angular position of thelever. As shown in FIG. 9, port 4 of the vacuum valve 160 is connectedby vacuum line 192 to port 2 of the control head vacuum valve 116. Port3 of valve 160 is connected by vacuum line 194 to port 8 of the controlhead vacuum valve 116. Port 2 of the vacuum valve 160 is connected byvacuum line 196 to a water control valve 198 which is opened by vacuumpressure to permit passage of engine coolant into heater core 44. Watercontrol valve 198 is located adjacent firewall 22 is FIG. 1 andregulates the coolant flow through one of two heater hoses 199(partially illustrated). Port 1 of the servo vacuum valve 160 isconnected by vacuum line 200 to port 6 of the control head vacuum valve1 16.

Referring again to FIG. 6, levers 162 and 166 are pivoted about axis 164by the linear movement of interconnected and superimposed arms 202 and204 within housing 158. Arms 202 and 204 are joined for movementtogether by a nut and bolt fastening means 206. An upstanding pin 208 onthe upper arm 202 engages an elongated slot 210 in lever 162 to pivotthe lever and rotate a portion of valve 160 about axis 164. A second pin212 on the lower arm 204 engages the lever 166 to rotate the lever andthe attached conductor plate 168 about axis 164. An actuating arm 216 isengaged at one end by the pin 212 and extends through an opening inhousing 158. Arm 216 is connected at another end to a crank arm of theair-mix damper 58 to pivot the damper into variable positions. A dustcover (not shown) is attached at locations 218 by bolts to enclose theaforementioned components in housing 158. Ports 1 through 4 of valve 160project through holes in the dust cover for exterior connection tovacuum lines.

The members 162, 166, 202, 204 and 216 are moved in housing 158 by adiaphragm 220 positioned in the interior of a power housing 222 which isattached to one end of housing 158 by twisted tabs 223. Housing 222 isformed by joining the edges of cup-shaped members 224 and 226 in themanner shown at 228. The outer peripheral edge of diaphragm 220 is heldbetween the edges of members 224 and 226 at joint 228. Arm 204 projectsthrough housing 158 and into the interior of housing 222 where it isattached to diaphragm 220. The diaphragm 222 extends across the interiorhousing 222 and forms a variable volume chamber 230 between it andmember 226. A spring 232 in chamber 230 normally presses the diaphragmagainst the end of member 224. A cup-shaped stiffening washer 234 isattached to the central region of diaphragm 220 and contacts spring 232.A vacuum outlet fitting 236 on member 226 extends into chamber 230.

When vacuum pressure is applied to the chamber 230 through outlet 236,diaphragm 220 and washer 234 move to the right against the force ofspring 232 to linearly move arms 202, 204, and 216. This movement of thearms produces rotational movement of levers 162 and 166 and rotates theair-mix damper 58. The extent of the movement of diaphragm 220 againstspring 232 is dependent upon the vacuum pressure strength applied tochamber 230. As will be revealed by later description, a weak vacuumpressure applied to chamber 230 corresponds to the maximum airconditioning mode of operation of the system. A relatively strong vacuumpressure applied to chamber 230 moves lever 162, lever 166 and arm 216to the right to effect the position of the system components for themaximum heating mode of operation. Intermediate vacuum pressures appliedto chamber 230 correspond to intermediate positions of air-mix damper 58to produce warmer or cooler air flow.

An electrically controlled vacuum transducer 238 (see FIGS. 8 and 9) hasan inlet port 240 connected by a vacuum line 242 to the outlet 236 ofthe power housing 222. An outlet 244 of transducer 238 is connected by avacuum line 246 to the vacuum storage tank 138. Vacuum pressure from theintake manifold of an internal combustion engine is transmitted throughvacuum line 136, check valve 134, vacuum line 140, storage tank 138, andvacuum line 246 to the vacuum transducer 238. The transducer 238 mixesair at atmospheric pressure with the vacuum pressure from the storagetank to create a decreased regulated vacuum pressure in line 242 andchamber 230 in response to a voltage signal input to the transducer.Reference is had to the U.S. Pat. No. 3,073,345, granted Jan. 15, 1963,in the name of N. R. l-Iagler, for a more detailed explanation of thestructure and operation of the vacuum transducer 238.

The vacuum transducer 238 receives a variable voltage signal from anamplifier 248 through a conductor 250. Another lead 252 grounds thetransducer 238. The amplifier 248 is supported on the underside of thecontrol head assembly 94 as shown in FIG. 7. Input power for amplifier248 is supplied from an automobile battery 254 through the ignitionswitch 256, a fuse 258, a conductor 260, to a conductor strip 262 oncircuit board 130. Hence the circuit extends from conductor strip 262through conductor 124 to another conductor strip 264 on circuit boardand from there through a conductor 266 to the amplifier 248.

Note that the conductor strips 262 and 264 are unconnected by conductor124 when the lever 96 of control head assembly 92 is placed in the offposition. Conductor 266 is the primary power input for amplifier 248. Asecondary power input 268 to the amplifier 248 extends between conductor266 at terminal 270 and the amplifier. Three thermistors A, B and C inseries in conductor 268 sense various temperature conditions in andabout the automobile and change resistance in inverse proportion totemperature variation. The resistance of the three thermistors in seriesinfluences the amplifier 248 to send a variable voltage signal throughconductor 250 to the vacuum transducer 238.

Thermistor A is an ambient temperature sensor positioned adjacent theair inlet 49 as shown in FIG. 1. Thermistor B is an air outlettemperature sensor positioned downstream from the air-mix damper 58.Thermistor C is an in-car temperature sensor located on the dash whereis senses the sum load on the automobile.

The net resistance of thermistors A, B and C is further varied to alterthe input to amplifier 248 by a manually adjustable rheostat 272.Rheostat 272 is electrically connected to amplifier 248 and is groundedby a conductor 274. The rheostat is part of the control head assembly 94as is shown in FIGS. 7 and 8 and is manually adjustable by rotation of acalibrated dial 276 which projects through face 98 of the assembly 94.The net resistance of thermistors A, B, C and the rheostat 272 effects aregulated voltage output from amplifier 248 which is applied totransducer 238 by conductor 250. The regulated voltage signal controlsthe vacuum pressure produced by the transducer 238. This controlledvacuum pressure is supplied to the servo-power assembly 156 throughvacuum line 242 to position its servo vacuum valve 160 and its conductorarm 172 in accordance with desired heating and cooling.

The internal connections of the vacuum ports and vent passages of thecontrol head vacuum valve 116 and of the servo vacuum valve 160 areshown in FIGS. 10 and 11 respectively. FIG. 10 shows the five alternateconditions of the valve 116, corresponding to the positions of lever 96.FIG. 11 shows the four alternate positions of the valve 160 as lever 162is pivoted from a maximum air conditioning position (counterclockwise tothe left in FIG. 6) to a maximum heating position (clockwise to theright in FIG. 9).

The graph in FIG. 14 reveals the various control functions of the systemplotted in relationship to the angular position of air-mix damper 58.The left hand ordinate of FIG. 14 corresponds to the position of damper58 in the maximum air conditioning mode of operation. The right handordinate of FIG. 14 corresponds to the position of damper 58 when it ispivoted to the maximum heating mode of operation. Note that the air-mixdamper 58 is held in the zero degree maximum air conditioning positionfor a portion of the extreme leftward movement of arm 216 as shown bythe labeling of the abscissa in FIG. 14. This delay of damper movementis caused by a sprung, relatively movable linkage (not shown) betweenthe arm 216 and the crank arm of the damper 58. For further details of asimilar arrangement reference is made to U.S. Pat. No. 3,263,739 toGaskill, et al issued Aug. 2, 1966.

As levers 162 and 166 in assembly 156 are pivoted from the maximum airconditioning position to the maximum heating position, conductor arms172 of assembly 156 are drawn across circuit board 170 as isschematically illustrated in FIGS. 9 and 14. The connection of conductorarms 172 alternately with the conductor strips 176, 178, 180 and 182regulates the speed of the blower motor 54. More particularly, theprimary blower motor circuit extends from battery 254 through ignitionswitch 256, fuse 258, conductor 260, a blower motor relay generallyindicated at 278, a conductor 280, a conductor 282, conductor arms 172,circuit board 170, conductors 284 and 286 to motor 54 and hence toground through a conductor 288. The blower motor relay 278 includes anormally open switch 290 in the conductor 280. Switch 290 is closed byenergization of a solenoid 292 whose leads are connected to a conductorstrip 294 of circuit board 130 by a conductor 296 and to a conductorstrip 298 of circuit board 130 by a conductor 300. Power is supplied tosolenoid 292 by a circuit from battery 254 through ignition switch 256,fuse 258, conductor 260, conductor strip 262, conductors 124, conductorstrip 294, conductor 296, solenoid 294, conductor 300 to the conductorstrip 298. When lever 96 of the control head assembly 94 is placed atthe fog or ice positions a circuit is completed by conductors 122 to aconductor strip 302 on the circuit board 130 which is grounded. Whenlever 96 is placed on the vent, ofi or low positions of the control headassembly 94, conductors 124 do not contact the conductor strip 294 andtherefore no power is applied to solenoid 292. Further when the lever 96is placed on the auto or high position, the conductors 122 do notinterconnect the conductor strips 298 and 302 to complete the circuitthrough the solenoid 292. However, the solenoid 292 may be energizedwhen the control lever 96 is placed in the auto or high positions byauxiliary grounding of conductor 300 through an incar switch 304 or aheater turn-on switch 306. The in-car switch 304 which is connectedbetween conductor 300 and ground immediately energizes the blower motorfor air conditioning operation whenever temperature of the passengercompartment exceeds a predetermined relatively high level. The heaterturn-on switch 306 which is connected between conductor 300 and theground delays energization of the blower motor during a heating mode ofoperation until the temperature of engine coolant rises to apredetermined warm level. It should be noted that a second switch 308 inthe blower motor relay 278 is closed by energization of solenoid 292.After switch 308 is closed by the solenoid 292, a current path isprovided through the solenoid, conductor 310 and switch 308 to groundindependently of conductor 122 and switches 304, 306. This lockingfeature in relay 278 prevents deenergization of the blower motor 54 byeither switches 304 or 306.

While the automobile is operated in an ambient exceeding a predeterminedtemperature, the air conditioning compressor 28 is continually operatedto dehumidify air within the plenum chamber 48. In FIG. 9, amagnetically actuated clutch pulley for the compressor 28 isschematically illustrated at 312. A bimetal ambient sensing switch 314controls energization of clutch 312 by completing a circuit from battery254 through ignition switch 256, fuse 258, conductor 260, bimetal switch314, clutch 312 to ground. To complement this continual compressoroperation and consequential dehumidifying, blower motor 54 iscontinually run at its lowest speed while ignition switch 256 is closed.More particularly, a closed circuit extends from battery 254 throughignition switch 256, a fuse 316, a conductor 318, the resistors of thecircuit board 170 in series, conductors 284 and 286, motor 54 to ground.As previously explained, the blower motor circuit is altered by movementof conductor arms 172 over circuit board 170 to produce increased blowermotor speed.

When lever 96 of the control head assembly 94 is placed in the high andice positions, a closed circuit bypasses the circuit board 170 of theservo-power assembly 156 to effect a high blower speed. This circuitextends from battery 254, through ignition switch 256, fuse 258,conductor 260, switch 290 of blower relay 278, conductor 280, aconductor 320, a conductor strip 322 on circuit board 130, conductors126 supported by lever 96, a conductor strip 324, a conductor 326 andconductor 286 to the blower motor 54 and hence through conductor 288 toground.

Pivotal movement of purge door 64 to close purge outlet 60 and openheater outlet 66 is effected by vacuum actuator 68 in response tosettings of the lever 96. As previously explained, it is desirable toopen the purge outlet 60 to the passenger compartment when the heatingand air conditioning system is inoperative. Conversely, it is desirableto open heater outlet 66 when the system is operative. FIG. 12 isolatesthe electrical and vacuum controls which position the purge door 64.Vacuum pressure is routed to port 1 of the control head vacuum valve 116by a vacuum line 132. As can be seen in FIG. 10, port 1 and port 3 ofvalve 116 are innerconnected in all positions of lever 96. A vacuum line142 extends from port 3 to the outlet of valve 144. Another vacuum line146 extends from the vacuum actuator 68 to an inlet of valve 144. Whenvalve 144 is open vacuum pressure is applied to actuator 68 through thevalve.

As shown in FIG. 13, valve 144 is a normally closed, electricallycontrolled valve having an outlet 328 and two inlets 330 and 332. Outlet328 is connected to vacuum line 142 for supplying vacuum pressure to thevalve 144. Inlet 330 and 332 are connected to vacuum lines 146 and 148respectively for supplying vacuum pressure to actuators and 68. Areciprocal valve element 334 within a bore 336 is normally biaseddownward by a spring 338 to cause an end 340 of valve element 334 toblock outlet passage 342. An electrical solenoid coil 344 surrounds thevalve element 334 and causes it to move upward against the force ofspring 338 when electrical energy is applied to the coil. Upwardmovement of valve element 334 causes an end 346 of the valve element 334to block a vent passage 348. Normally vent passage 348 communicatesinlets 330 and 332 with atmosphere by leakage between the noncircularvalve element 334 and bore 336. A filter 350 prevents dust from enteringvent passage 348. An outer casing 352 which protects the solenoid coil344 has vents 354 therethrough for cooling the coil. Accordingly, it canbe seen that when coil 344 is unenergized, end 344 of valve element 334blocks the outlet passage 342 and inlets 330 and 332 are incommunication with atmospheric pressure through vent 348. When coil 344is energized, vent passage 348 is blocked by end 346 of valve element334 and the outlet passage 342 is unblocked so inlets 330 and 332 aresupplied with vacuum pressure from outlet 328.

From FIG. 12, it is clear that when lever 96 of the control headassembly 94 is placed in vent, low, auto, high, fog or ice positions, anelectrical circuit extends from conductor 260 (which is the power inputline shown in FIG. 9) through conductor strip 262, conductors 124, aconductor strip 354, a conductor 356, to the valve 144 which is groundedby a conductor 358. Thus coil 344 of valve 144 is energized in all ofthe positions of lever 96 except the off position. Consequently, purgedoor 64 blocks heater outlet 66 and unblocks purge outlet 60 when lever96 is in the off position or when the ignition switch 256 is open. Atthe other positions of lever 96, the purge door 64 unblocks heateroutlet 66 and blocks purge outlet 60 in response to vacuum applied tothe actuator 68.This operation of purge door 64 in combination with theaforemen' tioned continual blower motor operation provides a desirableair flow through the plenum chamber 48 while the system is inoperative.

While the embodiment of the present invention as herein describedconstitutes a preferred form, it is to be understood that other formsmay be adapted.

What is claimed is as follows:

1. A heating and air conditioning system for an automobile passengercompartment comprising: hollow duct means forming an elongated plenumchamber for passing air therethrough; a warmed heater core within saidplenum chamber for heating air flowing through said plenum chamber; acooled evaporator core within said plenum chamber for cooling anddehumidifying air flowing through said plenum chamber; an inlet openingin said duct means for admitting air from said passenger compartmentinto one end of said elongated plenum chamber; outlet opening means insaid duct for discharging air from the other end of said elongatedplenum chamber into said passenger compartment; a blower within saidplenum chamber for drawing air through said inlet from said passengercompartment and discharging the air through said outlet means back intosaid passenger compartment; an electric motor powered by a battery forrotating said blower; and means including the automobile ignition switchfor energizing said blower motor for producing a continuous relativelylow volume of airflow through said plenum independently of the heatingand air conditioning controls.

2. A heating and air conditioning system for an automobile passengercompartment comprising: hollow duct means forming an elongated plenumchamber for passing air therethrough; a warmed heater core within saidplenum chamber for heating air flowing through said plenum chamber; acooled evaporator core within said plenum chamber for cooling anddehumidifying air flowing through said plenum chamber; an inlet in saidduct means for admitting air into one end of said elongated plenumchamber; a purge outlet in said duct means for discharging air from theother end of said elongated plenum chamber into the passengercompartment; another outlet in said duct means for discharging air fromsaid other end of said elongated plenum chamber into the passengercompartment; control means for blocking said last mentioned outlet andunblocking said purge outlet when the heating and air conditioningsystem is inactive and for unblocking said last mentioned outlet andblocking said purge outlet when the system is active; an electric motorpowered fan energized through the automobile ignition switch to cause acontinuous air flow into said inlet means, through said plenum chamberand alternatively out said purge outlet and said other outlet into thepassenger compartment.

3. The heating and ventllatlng system as set forth in Claim 2,

wherein said duct means extends through a firewall of the automobile todischarge air into the front of the passenger compartment, said purgeoutlet facing in a direction away from the passenger compartment towardthe firewall for preventing a direct flow of air therethrough ontopassengers in the passenger compartment.

4. A heating and air conditioning system as set forth in Claim 2,wherein said purge outlet has a smaller flow area than said otheroutlet.

5. A heating and air conditioning system as set forth in Claim 2,wherein said purge outlet and said other outlet are adjacent one anotherthrough said duct means, said control means including a door hinged atone edge to said duct means between said purge outlet and said otheroutlet and pivotal to alternately block said outlets.

1. A heating and air conditioning system for an automobile passenger compartment comprising: hollow duct means forming an elongated plenum chamber for passing air therethrough; a warmed heater core within said plenum chamber for heating air flowing through said plenum chamber; a cooled evaporator core within said plenum chamber for cooling and dehumidifying air flowing through said plenum chamber; an inlet opening in said duct means for admitting air from said passenger compartment into one end of said elongated plenum chamber; outlet opening means in said duct for discharging air from the other end of said elongated plenum chamber into said passenger compartment; a blower within said plenum chamber for drawing air through said inlet from said passenger compartment and discharging the air through said outlet means back into said passenger compartment; an electric motor powered by a battery for rotating said blower; and means including the automobile ignition switch for energizing said blower motor for producing a continuous relatively low volume of airflow through said plenum independently of the heating and air conditioning controls.
 2. A heating and air conditioning system for an automobile passenger compartment comprising: hollow duct means forming an elongated plenum chamber for passing air therethrough; a warmed heater core within said plenum chamber for heating air flowing through said plenum chamber; a cooled evaporator core within said plenum chamber for cooling and dehumidifying air flowing through said plenum chamber; an inlet in said duct means for admitting air into one end of said elongated plenum chamber; a purge outlet in said duct means for discharging air from the other end of said elongated plenum chamber into the passenger compartment; another outlet in said duct means for discharging air from said other end of said elongated plenum chamber into the passenger compartment; control means for blocking said last mentioned outlet and unblocking said purge outlet when the heating and air conditioning system is inactive and for unblocking said last mentioned outlet and blocking said purge outlet when the system is active; an electric motor powered fan energized through the automobile ignition switch to cause a continuous air flow into said inlet means, through said plenum chamber and alternatively out said purge outlet and said other outlet into the passenger compartment.
 3. The heating and ventilating system as set forth in Claim 2, wherein said duct means extends through a firewall of the automobile to discharge air into the front of the passenger compartment, said purge outlet facing in a direction away from the passenger compartment toward the firewall for preventing a direct flow of air therethrough onto passengers in the passenger compartment.
 4. A heating and air conditioning system as set forth in Claim 2, wherein said purge outlet has a smalleR flow area than said other outlet.
 5. A heating and air conditioning system as set forth in Claim 2, wherein said purge outlet and said other outlet are adjacent one another through said duct means, said control means including a door hinged at one edge to said duct means between said purge outlet and said other outlet and pivotal to alternately block said outlets. 